House Republicans saw a significant drop in fundraising last month. The National Republican Campaign Committee hauled in $9.3 million in June compared to $4.6 million in July.

Across the aisle, the Democratic Congressional Campaign Committee raised $12 million in July despite the release of hacked emails from the Democratic National Committee and scandal surrounding former chairwoman Rep. Debbie Wasserman Schultz's support of Hillary Clinton over Vermont Sen. Bernie Sanders.

But NRCC's fundraising has consistently trailed the DCCC's and currently stands $19 million behind the Democrats' $133 million.

The GOP's fundraising plunge could put the Republican majority at risk in November if toss-up races do not have the financial backing necessary to win. But the reason behind it may be a mix of causes, including Republican nominee Donald Trump's sometimes controversial remarks, according to experts.

"Some of the media coverage coming out of the convention, and particularly during the Democratic convention, may have dampened some fundraising enthusiasm for us," NRCC Executive Director Rob Simms told the Wall Street Journal.

Donors may be more focused on maintaining the Senate than the House because of its greater importance in the legislative process. The House is currently controlled by Republicans by a 247-186 margin. The upper chamber has 54 Republicans, 44 Democrats and two Independents who caucus with the Democrats. Control of it could prove necessary if Clinton wins in November and wants to hold hearings on a Supreme Court justice nominee.